During a production line manufacturing process such as a part welding line or a part assembly line, on occasion, defective parts are manufactured. It is important to identify and remove these defective parts and ensure that they remain segregated from good parts so that they are not subsequently incorporated into a finished article sold to a consumer or used. It is advantageous to identify defective parts as soon as possible so that those parts can be removed from the production line before additional expenses associated with further machining or assembly are incurred and prior to incorporation of the defective part into a larger assembly.
There have been a number of systems generated, particularly for resistance welding, which inspect a part automatically as the part is being processed. In applications such as resistance welding, non-destructive physical testing is difficult, if not impossible, to conduct. For this reason, a number of inspection systems have been developed to identify effectively welded or formed parts automatically during and after the part forming process.
Examples of such systems are shown in U.S. Pat. No. 4,387,064 to Werderitch et al., U.S. Pat No. 4,562,330 to Hamilton, U.S. Pat. No. 5,197,186 to Strong et al., U.S. Pat. No. 5,128,507 to Drake, U.S. Pat. No. 5,254,828 to Stiebel and a series of U.S. patents obtained by the present applicant: U.S. Pat. Nos. 4,542,777, 4,684,778, 5,220,145, and 5,288,968. The previously identified systems identify the defective parts but frequently require the operator to remove the defective part from the production line and place it in a defective part bin. U.S. Pat. No. 4,387,064 automatically places the defective parts in a defective part bin. Similarly, U.S. Pat. No. 5,186,887, which discloses a system for inspecting nuclear fuel pellets, automatically deposits defective pellets in an appropriate box.
One of the problems that the present invention solves is that machine operators frequently incorrectly assume that the automatic parts inspection operation committed an error when a part which looks perfectly good is rejected. On occasion, operators will pass the rejected part, as opposed to removing the part from the production line, which ultimately causes defective parts to be incorporated into finished goods. Inclusion of defectively welded parts into a production vehicle, for example, can result in expensive warranty repairs or product recall. On some occasions, the defectively welded part will fail during a subsequent manufacturing operation and will not even make it out of the plant. For example, weld nuts which are improperly attached to an assembly may subsequently break off during the nut tapping process or when a fastener is subsequently attached. If the product incorporating the weld nut is in an advance stage of assembly, the cost and expense for repairing a defectively welded part can be significant.
Accordingly, it is an object of the present invention to provide a method and apparatus for ensuring that defective parts which are identified at an inspection station in a production line are promptly removed and placed in a defective part containment box.
It is another object of the present invention to provide a method and apparatus for marking defective parts prior to placement in the part containment box so that a manufacturer can ensure that all parts identified as being defective are properly discarded.
Yet another object of the present invention is to provide a method and apparatus which forecloses the possibility of a situation occurring where a part identified as being defective is passed on as a good part by the production operator who, with good intentions after a visual inspection, incorrectly believes that the part is not defective.
Another object of the present invention is to provide a method and apparatus for identifying parts exhibiting a predetermined characteristic at a production line inspection station which requires the identified part to be removed and securely stored prior to resuming operation of the production line.